Direct Charge-Transfer Transition Drives Triplet Generation and Photon Upconversion in 2D Hybrid Perovskites

Area of Science:

• Materials Science
• Solid-State Physics
• Photochemistry

Background:

• Organic semiconductor-incorporated 2D hybrid perovskites offer novel properties via organic-inorganic interfaces.
• Interfacial optical phenomena and excited-state processes in these materials are largely unexplored.

Purpose of the Study:

• To investigate interfacial optical phenomena and excited-state processes in organic semiconductor-incorporated 2D hybrid perovskites.
• To identify new photophysical pathways and functionalities at the organic-inorganic interface.

Main Methods:

• Time-resolved spectroscopy
• Ab initio calculations
• Investigation of (BTm)2PbI4 as a model system

Main Results:

• Unambiguous identification of a below-gap interfacial charge-transfer (CT) transition with type II energy level alignment.
• Correlation between CT transition oscillator strength and structural distortion, highlighting the role of dynamic lattice disorder.
• Discovery of a new excited-state pathway enabling direct molecular triplet generation and photon upconversion with 0.42 eV energy gain.

Conclusions:

• Established emergent optical activity and photophysical pathways at organic-inorganic interfaces in 2D hybrid perovskites.
• Demonstrated a novel strategy for triplet sensitization and photon upconversion using below-gap photons.
• Highlighted the potential of harnessing interfacial CT transitions for advanced optoelectronic functionalities.